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Ocean study raises questions about impact of climate change

Posted January 5, 2004; 12:57 a.m.

by quinones

A study has shown that marine life around the world is surprisingly dependent on a single ocean circulation pattern in the Southern Hemisphere where nutrient-rich water rises from the deep and spreads across the seas.

The results suggest that ocean life may be more sensitive to climate change than previously believed because most global warming predictions indicate that major ocean circulation patterns will change. While oceanographers have identified many ocean circulation patterns, the study found that three-quarters of all biological activity in the oceans relies on this single pattern.

"When we shut off this one pathway in our models, biological productivity in the oceans drops to one-quarter of what it is today," said
Jorge Sarmiento
, a Princeton oceanographer who led the study published in the Jan. 1, 2004, issue of Nature. Marine organisms account for half all biological productivity on Earth.

The discovery helps oceanographers settle a longstanding question about what keeps the world's oceans fertile. Most biological activity in the ocean is concentrated near the surface where an abundance of microorganisms perform photosynthesis and support marine food chains. These organisms and their byproducts slowly sink from the surface, decomposing along the way and carrying nutrients to the deep ocean. Until now, it has not been clear how the surface becomes replenished with the nutrients that seemed lost to the deep ocean.